Radiation Measurement and Instrumentation Flashcards
7 cards from real CHP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Radiation Measurement and Instrumentation flashcards as text
The W-value for air (approximately 34 eV/ion pair) is used to convert:
Answer: Energy deposited to number of ion pairs created
The W-value (mean energy per ion pair) converts total energy deposited in a gas into the number of ion pairs produced, which is proportional to the measured charge.
A Fano factor less than 1 in semiconductor detectors indicates:
Answer: Statistical fluctuations are sub-Poissonian, giving better resolution than expected
A Fano factor F < 1 means the variance in ion-pair creation is smaller than Poisson statistics predict, which is why HPGe resolution exceeds the Poisson limit.
Compton suppression in a gamma-ray spectrometer system is achieved by:
Answer: Surrounding the primary detector with an annulus detector in anticoincidence
An anticoincidence annulus detector vetoes events where a Compton-scattered photon escapes the primary detector, reducing the Compton continuum.
The quench gas in a Geiger-Müller tube serves to:
Answer: Absorb UV photons and positive ions to terminate the discharge
The quench gas (e.g., halogen or organic vapor) absorbs UV photons and neutralizes positive ions, preventing spurious secondary discharges.
An OSLD (optically stimulated luminescence dosimeter) differs from a TLD primarily in that readout is performed by:
Answer: Exposing the crystal to a specific wavelength of light
OSLDs are read by stimulating the crystal with laser light of a specific wavelength rather than by thermal heating as in TLDs.
Plutonium-239 alpha particle emission is most accurately measured in the field using a:
Answer: Thin-window proportional counter with low-energy response
Alpha particles have very short ranges in air and matter, requiring a thin-window (or windowless) proportional counter to detect them effectively.
The moderation ratio used in Bonner sphere spectrometry refers to the ratio of:
Answer: Polyethylene sphere diameter to bare detector diameter
Bonner spheres of different polyethylene diameters produce response functions that peak at different neutron energies; the sphere diameter relative to the bare detector defines each channel's energy sensitivity.